The present invention relates to a roll control system for an automotive vehicle, and more specifically relates to a vehicle roll control system which takes account of changes in vehicle body laden weight.
The present invention has been described in Japanese patent application Ser. No. 61-059032 (1986), filed by an applicant the same as the entity assigned or owed duty of assignment of the present patent application; and the present patent application hereby incorporates into itself by reference the text of said Japanese patent application and the claims and the drawings thereof; a copy is appended to the present application.
Further, the present inventors wish hereby to attract the attention of the examining authorities to copending patent application Ser. Nos. 921,138, 921,251 (U.S. Pat. No. 4,693,493) 921,450, 921,451, and 921,468 which may be considered to be material to the examination of the present patent application.
In general, in the operational conditions where a vehicle such as an automobile turns at a speed not less than a particular determinate turning speed value, the body of the vehicle experiences rolling, i.e. the vehicle body inclines in the radially outward direction, and this rolling results in deterioration of the drivability of the vehicle.
In order to cope with the above problem, as shown, for example, in Japanese Patent Laying Open Publication Ser. No. Sho 59-120509 (1984) and in the specification of Japanese patent application Ser. No. Sho 59-172416 (1984), neither of which is it hereby intended to admit in any way as prior art to the present application except to the extent in any case mandated by applicable law, it has been conceived of, when the vehicle is being driven around a curve or corner, to adjust to high the hardness and softness characteristic of the suspension means of the vehicle, i.e. the resistance of the shock absorbers or the springing effect of the springs thereof.
As another approach--as described in the specifications of, for example, Japanese patent applications Ser. Nos. Sho 60-235659, Sho 60-235660, and Sho 60-235661, which are applications filed by at least one applicant the same as the entity assigned or owed duty of assignment of the present patent application, and the subject matters of some or all of which are included in the above identified Patent Applications which are copending with the present Patent Application as described above, but which it is not hereby intended to admit in any way as prior art to the present application except to the extent in any case mandated by applicable law--there have been proposed to fit to a vehicle various types of vehicle height adjustment type roll control systems comprising: a plurality of actuators which are provided for resiliently suspending the vehicle wheels from its body and are adapted to increase or decrease vehicle height at locations corresponding to the associated vehicle wheels as respective results of supplying or discharging working fluid to or from variable volume working fluid chambers of said actuators; a plurality of working fluid supplying and discharging means which are provided corresponding to the actuators and which serve to supply or discharge the working fluid to or from said actuators; a vehicle speed detecting means for detecting the road speed of the vehicle; a steering angle detecting means for detecting the steering angle of the vehicle; and a control means for predictingly computing the roll angle of the vehicle body based upon the vehicle speed and the steering angle as sensed by these detecting means therefor, and for in accordance with this predicted roll angle, when said predicted roll angle is greater than a determinate value, controlling the working fluid supplying and discharging means so as to reduce the rolling of the vehicle body, so as thus previously and predictingly to keep said vehicle body roll within a predetermined range. Also there have been proposed to fit similar vehicle height adjustment systems, in which the differences between the actual vehicle heights at its various wheels and certain reference vehicle heights are reduced to be within predetermined ranges, again so as thereby similarly previously and positively to prevent the vehicle body from rolling.
In a vehicle equipped with such a vehicle height adjustment system as described above, however, when the vehicle is directed around a curve or corner, then the so called "centrifugal force" which causes the body roll is in fact of a force magnitude proportional to the current value of the mass of the vehicle--more exactly, to the current value of the first moment of the mass of the sprung portion of the vehicle (which excludes the unsprung mass thereof but includes the weight of passengers therein and of cargo, accessories, fuel and the like) about its roll axis--and the rolling of the vehicle body is caused by this "centrifugal force" and by so called "inertial forces" set up by acceleration and deceleration of the vehicle. These "inertial forces" are also of force magnitudes proportional to the current value of said sprung mass of the vehicle. Accordingly, even for cases of the vehicle turning around a corner or curve of the same radius at the same speed and in the same conditions of vehicle acceleration or deceleration, the amount of vehicle body rolling which occurs will vary, sometimes quite dramatically, according to the current value of said total sprung mass of the vehicle.
However, since in such vehicle roll control systems not according to the present invention as described above it is not particularly performed to take any account of the total sprung mass of the vehicle, or to change any reference values in the calculation for controlling the amount of vehicle body rolling, i.e. for switching over the hardness and softness characteristic of the suspension means of the vehicle (the resistance of the shock absorbers or the springing effect of the springs thereof) or for switching over the roll control of the vehicle to its mode (when said predicted roll angle is greater than a determinate value) in which it controls the working fluid supplying and discharging means so as to reduce the rolling of the vehicle body so as previously and predictingly to keep said vehicle body roll within a predetermined range, therefore inevitably the roll control for the vehicle body cannot be always properly achieved, particularly in the case of a vehicle such as a bus or a truck or the like in which the variations of loading are relatively great as compared with a passenger car. In such a case, the drivability and the controllability and the comfortability of the vehicle are deteriorated, and the cornering and the road holding characteristics thereof may also suffer.